Controlled lowering of a polymers glass transition temperature

ABSTRACT

Processes for lowering the glass transition temperature of a polymeric compound relative to the glass transition temperature of a control polymeric compound are disclosed. The methods include the formation of a precursor composition comprising precursor compounds to the polymeric compound dispersed or dissolved in a solvent system. The compounds are partially or fully cured in the presence of the solvent system, which is then substantially removed. After further curing, where necessary, the resulting cured polymeric compound is essentially free of plasticizers, but still has a decreased glass transition temperature relative to the glass transition temperature of a control polymeric compound. Articles of manufacture comprising such polymeric compounds are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the priority benefit of U.S. ProvisionalPatent Application Ser. No. 61/453,579, filed Mar. 17, 2011, entitledCONTROLLED LOWERING OF A POLYMER'S GLASS TRANSITION TEMPERATURE WITHOUTTHE USE OF PLASTICIZERS, incorporated by reference in its entiretyherein.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under contract#DE-NA0000622, awarded by the United States Department of Energy. TheUnited States government has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods of lowering the glasstransition temperature of a polymer, and articles formed thereby.

2. Description of Related Art

One of the more important fundamental properties of a polymer is itsglass transition temperature (Tg). The exact temperature of a polymer'sTg is dictated by a wide variety of factors, including the monomers usedto make the polymers, the presence of large molecular moieties attachedto the polymer's main chain, the amount and type of cross-links foundwithin the polymers, and the presence of a plasticizer, etc. Above itsTg, a polymer is relatively soft and pliable. Below its Tg, a polymerbehaves like a glassy solid. Plasticizers are well known to lower the Tgof a given polymer by creating an environment within the polymer matrixwhere the polymer chains can slide past one another more easily. The useof plasticizers is ubiquitous throughout the world of commercialpolymers, with their addition to a polymer matrix being common forreducing a polymer's Tg. However, in many instances it would be usefulto lower the Tg of a given polymer matrix without needing to use aplasticizer or without the need for the plasticizer to be present in thepolymer matrix. Plasticizers can be volatile, evaporating over time andthus also changing the performance of the polymer into which it has beenincorporated. Other plasticizers have been shown to, or are suspected tobe, toxic. The elimination of such plasticizer from polymer productswould be beneficial, if there was a way to controllably lower the Tg ofa polymer without the need for a plasticizer in the end product.

SUMMARY OF THE INVENTION

The present invention is broadly concerned with a method of lowering theglass transition temperature of a polymeric compound (polymer) relativeto a control, wherein the control has a first glass transitiontemperature. The method comprises providing a precursor composition,which comprises a precursor compound dispersed or dissolved in a solventsystem. The precursor compound is selected from the group consisting ofmonomers (including chain extenders), oligomers, pre-polymers, polymers,and combinations thereof. The precursors to the polymeric compound arecured in the presence of the solvent system to yield a cured polymernetwork or partially cured polymer resin. The cured polymer network orpartially cured polymer resin is swollen with the solvent. The solventsystem is then substantially removed to yield a cured polymeric compoundor dried polymer resin, which may be further cured to yield thepolymeric compound, if desired. The resulting fully cured polymericcompound (polymer) has a second glass transition temperature that islower than the first glass transition temperature.

An article of manufacture comprising a polymeric compound is alsoprovided. Advantageously, the polymeric compound has a decreased glasstransition temperature relative to a control, and is essentially free ofplasticizer.

The present invention is applicable in a wide variety of polymericcompounds. Nearly anything made or manufactured from such polymers couldeffectively have its glass transition temperature lowered without theneed for the plasticizer to be present in the final article.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a graph of the rheology data from the Model Epoxies preparedin Example 1;

FIG. 2 is a graph of the rheology data from the Model Epoxies preparedin Example 1, after being subjected to additional heating under vacuum;

FIG. 3 is a graph of thermogravimetric analysis (TGA) results of thesamples from Example 1;

FIG. 4 is a graph of the rheology data from the Model Epoxies preparedin Example 1, and subjected to various cure times;

FIG. 5 is a graph showing the % weight loss of the Model Epoxiesprepared in Example 1, and subjected to various cure times;

FIG. 6 is a graph of the rheology data from the EN8 urethanes preparedin Example 2; and

FIG. 7 is a graph of the rheology data from the EN8 urethanes preparedin Example 2, and subjected to various cure times.

DETAILED DESCRIPTION

The present invention is concerned with the controlled manipulation ofthe Tg of a polymeric compound, methods of carrying out the same, andarticles of manufacture prepared therefrom. Suitable polymeric compoundsthat can be modified using the invention include those with precursorcompounds that are substantially soluble in a solvent system and can becured in the presence of the solvent system. In addition, after beingcured, the resulting polymeric network preferably remains swollen by thesolvent system, which can then be substantially removed, as discussed inmore detail below. Suitable polymeric compounds would include manythermoplastic polymers and most thermosetting polymers (i.e., prepolymermaterials or compounds that undergo an irreversible change upon fullycuring—typically from a soft solid or viscous state to an infusible,insoluble polymer network, once fully cured). Exemplary thermosettingcompounds (i.e., A-stage, unreacted resins) for use in the inventivemethods include, without limitation, monomers, oligomers, pre-polymersand/or polymers of epoxies, urethanes, silicones, cyanoacrylates,vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde,urea-formaldehyde, imides, esters, cyanate esters, allyl resins, andcombinations thereof. Suitable chain extenders that can be used toprepare the polymeric compound include diols, dicarboxylic acids,diamines, diacrylates, and the like. Exemplary thermoplastic compoundsfor use in the inventive methods include acrylonitrile butadienestyrene, polymethylmethacrylate, cyclic olefin copolymer, ethylene vinylacetate, ethylene vinyl alcohol, fluoroplastics, liquid crystalpolymers, polyacrylates, polyacrylonitrile, polyamide, polyamide-imide,polyaryletherketone, polybutadiene, polyisoprene, styrene butadienerubber, conjugated diene elastomers, polybutylene, polybutyleneterephthalate, polycaprolactone, polychlorotrifluoroethylene,polycyclohexylene dimethylene terephthalate, polycarbonate,polyhydroxyalkanoates, polyketone, polyester, polyethylene,polypropylene, polystyrene, polyetheretherketone, polyetherketoneketone,polyetherimide, polyethersulfone, polysulfone, chlorinated polyethylene,polyimide, polylactic acid, polymethylpentene, polyphenylene oxide,polyphenylene sulfide, polyphthalamide, polysulfone, polytrimethyleneterephthalate, polyurethane, polyvinyl acetate, polyvinyl chloride,polyvinylidene chloride, styrene acrylonitrile, and the like.

In one aspect of the inventive method, the precursor compounds (i.e.,monomers, chain extenders, oligomers, pre-polymers, polymers, andcombinations thereof) are dispersed or dissolved in a solvent system toform a precursor composition. The precursor composition is preferablyformed by mixing the ingredients together under ambient conditions (˜25°C., ˜14.7 psi or ˜1 atm) for a sufficient time period to uniformlydisperse or dissolve the compounds in the solvent system. The level ofprecursor compounds used in the composition will vary, but willtypically range from about 50% to about 99.9% by weight, preferably fromabout 70% to about 99.5% by weight, and more preferably from about 75%to about 99% by weight, based upon the total weight of the compositiontaken as 100% by weight. The solvent system can be present in thecomposition at a level of from about 0.1% to about 50% by weight,preferably from about 0.5% to about 30% by weight, and more preferablyfrom about 1% to about 25% by weight, based upon the total weight of thecomposition taken as 100% by weight.

Suitable solvent systems will depend upon the compounds used in theprecursor composition. A preferred solvent system will be one in whichthe precursors to the polymeric compound can be dissolved or dispersed(i.e., the polymer material, before curing, is relatively, andpreferably substantially, soluble in the solvent system), and one inwhich, after being cured, the resulting polymeric compound remainsswollen by the solvent system. A preferred solvent system will alsocontain one or more solvents that have a sufficiently high boiling pointto be workable without evaporating (i.e., not too volatile), but willultimately volatize (evaporate) at a temperature below the degradationtemperature of the polymeric compound. More specifically, a suitablesolvent system will have a boiling point of from about 25° C. up toabout the T₅ temperature of the polymeric compound, preferably fromabout 35° C. up to a temperature that is about 20° C. lower than the T₅temperature of the polymeric compound, and more preferably from about50° C. up to a temperature that is about 50° C. lower than the T₅temperature of the polymeric compound. The “T₅ temperature” of apolymeric compound is a measure of its thermally stability, which isdefined as the temperature at which less than 5% weight loss is observedin the polymeric compound by TGA, when heated to that temperature for atleast about 10 minutes (under nitrogen). For example, the Model Epoxyformed in Example 1 has a T₅ temperature of about 190° C. Thus,preferred solvent systems for use with the Model Epoxy will have aboiling point of from about 25° C. to about 190° C., preferably fromabout 35° C. to about 170° C., and more preferably from about 50° C. toabout 140° C. Similarly, the T₅ temperature of the EN8 polyurethaneformed in Example 2 is about 280° C. Thus, preferred solvent systems foruse with the EN8 polyurethane will have a boiling point of from about25° C. to about 280° C., preferably from about 35° C. to about 260° C.,and more preferably from about 50° C. to about 230° C.

Exemplary solvents and their boiling points include, without limitation,acetic acid (118° C.), acetic acid anhydride (139° C.), acetone (56.3°C.), acetonitrile (81.6° C.), benzene (80.1° C.), iso-butanol (107.7°C.), n-butanol (117.7° C.), tert-butanol (82.5° C.), carbontetrachloride (76.5° C.), chlorobenzene (131.7° C.), chloroform (61.2°C.), cyclohexane (80.7° C.), cyclopentane (49.3° C.), dichloromethane(39.8° C.), dioxane (101° C.), ethanol (78.3° C.), ethyl acetate (77.1°C.), ethylene dichloride (83.5° C.), heptane (98.4° C.), n-hexane (68.7°C.), hydrochloric acid (84.8° C.), methyl ethyl ketone (79.6° C.),methanol (64.7° C.), methyl tert-butyl ether (55.2° C.), iso-propanol(82.3° C.), n-propanol (97.2° C.), pyridine (115.3° C.), tetrahydrofuran(66° C.), toluene (110.6° C.), trifluoroacetic acid (71.8° C.), water(100° C.), dimethyl acetamide (166.1° C.), dimethyl formamide (153° C.),pentane (36.1° C.), diethyl ether (34.6° C.), dimethyl sulfoxide (189°C.), ethyl ether (34.6° C.), ethylene glycol (197.5° C.), petroleumether (35-60° C.), and the like. Solvent mixtures may also be used inthe solvent system.

Additional optional ingredients can be dispersed or dissolved in thesolvent system with the compound. Such optional ingredients includecuring (crosslinking) agents, including diols, fillers, nanofillers,catalysts, processing aids, binders, pigments, antioxidants, antifungalagents, metal oxides, plasticizer, and the like. Exemplary curing agentswill also depend on the polymeric compound used in the composition, butincludes amines, peroxides, and sulfur for vulcanization. When present,the level of curing agent will typically range from about 0.001% toabout 10% by weight, preferably from about 0.01% to about 8% by weight,and more preferably from about 0.1% to about 6% by weight, based uponthe total weight of the composition taken as 100% by weight. Whenpresent, the level of fillers will typically range from about 0.1% toabout 25% by weight, preferably from about 0.5% to about 20% by weight,and more preferably from about 1% to about 15% by weight, based upon thetotal weight of the composition taken as 100% by weight. When present,the level of nanofillers will typically range from about 0.1% to about20% by weight, preferably from about 0.5% to about 15% by weight, andmore preferably from about 1% to about 10% by weight, based upon thetotal weight of the composition taken as 100% by weight.

The precursor composition is then subjected to a curing process. Inparticular, the precursor compounds are first cured in the presence ofthe solvent system (i.e., the solvent system is not substantiallyremoved during the curing process; rather, the polymeric compoundremains swollen by the solvent system during the curing reaction).Depending upon the boiling point of the solvent system and the polymericcompound materials involved, initial curing can take place under ambienttemperatures and/or pressures or elevated temperature (˜25-300° C.)and/or vacuum pressure (˜1E⁻⁹−200 psi). Preferably, the precursorcompounds are cured under ambient conditions. Curing is preferablycarried out for a time period of from about 0.001 to about 48 hours,more preferably from about 0.01 to about 24 hours, and even morepreferably from about 0.1 to about 16 hours. The polymeric compound doesnot need to completely cure in the presence of the solvent and may bepartially cured, meaning that the reacting ingredients in the precursorcomposition cure to the point of vitrification (i.e., B-stagethermoset). In other instances, the polymeric compound may be completelycured in the presence of the solvent system, but will remain swollenwith solvent. It will also be appreciated that references herein to“fully” or “completely” curing refer to substantially complete(approaching 100%) curing of the resin, although those skilled in theart will appreciate that 100% curing does not actually occur; rather,the cure reaction continues over time in many polymer systems, includingthe formation of new crosslinks as aging of the resin begins takingplace.

The solvent system is then substantially removed from the fully curedpolymeric compound or partially cured polymer resin. As used herein,“substantially removed,” means that at least about 99% by weight of thesolvent system is removed, and preferably at least about 99.9% by weightremoved, based upon the total weight of the initial solvent systemamount in the precursor composition, taken as 100% by weight. It will beappreciated that the solvent system can be removed from the curedpolymeric compound or resin using heat (to speed up evaporation), vacuumpressure, CO₂ extraction, freeze-drying, lyophilization, sublimation,centrifugation, and the like, and any combination thereof. In oneaspect, the solvent system is removed/evaporated by heating to atemperature greater than or equal to the boiling point of the solventsystem (preferably from about 25 to about 300° C.), for a time period offrom about 0.5 to about 48 hours (and preferably for about 1 to about 16hours).

The substantially dried polymer resin, if only partially cured in theabove process, can then be subjected to further curing to fully cure thecomposition (i.e., C-stage, cross-linked polymer network). This furthercuring may also aid in the removal of residual solvent remaining in thepolymeric compound. It will be appreciated that these parameters mayvary greatly depending upon the solvent system and the polymericcompounds involved. Typical curing temperatures will range from about25° C. to about the T₅ temperature of the polymeric compound, preferablyfrom about 25° C. to about 300° C., and more preferably from about 30°C. to about 200° C., at time periods of from about 0.1 to about 48hours, preferably from about 0.1 to about 10 hours, and more preferablyfrom about 0.5 to about 5 hours. Those of ordinary skill in the art willappreciate that during this process, the polymeric compound can becooled for a period of time (about 0.1 to about 24 hours) under ambientconditions, and then reheated (according to the ranges above), dependingupon the polymeric compound involved. In other words, the various stagesof the curing process may be repeated, as desired for the particularpolymeric compound being formed. Any stage of the curing process mayalso be carried out under vacuum to further facilitate removal of thesolvent system. The fully cured polymeric compound can also be subjectedto further heat and/or vacuum treatments for a time period of from about0.1 to about 48 hours to remove residual solvent, as desired. It will beappreciated that although the present invention is described primarilywith respect to heat curing, at any stage of the process describedherein, curing may be carried out using any suitable alternative curemechanism, including e-beam, radiation, and/or vulcanization.

It will be appreciated that during curing, the precursor composition canbe formed into the desired shape and/or size, depending upon the finalarticle to be formed, using any suitable technique, such as molding(e.g., resin transfer molding, compression molding, injection molding,etc.), extrusion, and/or pultrusion. The precursor composition can alsobe laminated and/or used to impregnate a fiber (woven or nonwoven)reinforcement before fully curing.

Advantageously, the cured polymeric compound will have a modified Tgthat has been decreased relative to the Tg of a control polymericcompound. Preferably, the modified Tg is at least about 5° C. lower thanthe Tg of a control polymeric compound, more preferably at least about10° C. lower, and even more preferably at least about 15° C. lower thanthe Tg of a control polymeric compound. A “control” polymeric compound,as used herein, refers to the same polymeric compound as the polymericcompound modified according to the invention, but in its native,non-modified state, formed without the use of plasticizers or otheragents or special processing parameters that modify the Tg of thepolymeric compound. In other words, the Tg of a control polymericcompound is what the Tg of the polymeric compound according to theinvention would have been, had that polymeric compound not beensubjected to the inventive methods. Thus, one advantage of the inventionis that the Tg-lowering effects of the inventive process remain, evenafter the solvent has been substantially removed from the system.Accordingly, another advantage of the present invention is that thefully cured polymeric compound is essentially free of plasticizer, whichmeans that the fully cured polymeric compound comprises less than about1% by weight plasticizer, more preferably less than about 0.5% by weightplasticizer, and even more preferably less than about 0.1% by weightplasticizer, based upon the total weight of the fully cured polymericcompound taken as 100% by weight. The present invention achieves thebenefits of polymeric compounds conventionally formulated usingplasticizers, without the drawbacks of plasticizer in the finalpolymeric compound.

Exemplary articles of manufacture that can benefit from the presentinvention include, without limitation, molded articles, pads, o-rings,gaskets, mats, cushions, foams, fibers, fabric, hoses, tubing, belts,tires, bladders, and the like.

Additional advantages of the various embodiments of the invention willbe apparent to those skilled in the art upon review of the disclosureherein and the working examples below. It will be appreciated that thevarious embodiments described herein are not necessarily mutuallyexclusive unless otherwise indicated herein. For example, a featuredescribed or depicted in one embodiment may also be included in otherembodiments, but is not necessarily included. Thus, the presentinvention encompasses a variety of combinations and/or integrations ofthe specific embodiments described herein.

As used herein, the phrase “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing or excludingcomponents A, B, and/or C, the composition can contain or exclude Aalone; B alone; C alone; A and B in combination; A and C in combination;B and C in combination; or A, B, and C in combination.

The present description also uses numerical ranges to quantify certainparameters relating to various embodiments of the invention. It shouldbe understood that when numerical ranges are provided, such ranges areto be construed as providing literal support for claim limitations thatonly recite the lower value of the range as well as claim limitationsthat only recite the upper value of the range. For example, a disclosednumerical range of about 10 to about 100 provides literal support for aclaim reciting “greater than about 10” (with no upper bounds) and aclaim reciting “less than about 100” (with no lower bounds).

EXAMPLES

The following examples set forth methods in accordance with theinvention. It is to be understood, however, that these examples areprovided by way of illustration and nothing therein should be taken as alimitation upon the overall scope of the invention.

Example 1 Model Epoxy A. Increasing Amounts of THF Added to Model Epoxy

A series of model epoxy formulations were prepared with increasingamounts of tetrahydrofuran (THF) solvent (boiling point 66° C.). Acontrol sample without THF was also made. The samples were prepared byweighing the desired amount of EPON® 828 (standard Bisphenol-A epoxyresin) into a small aluminum weighing dish, to which was added thedesired amount of THF (Table 1). The THF was carefully mixed into theEPON® 828 using a wooden tongue depressor that had been split the longway. Care was taken in mixing to minimize the evaporation of THF. To theEPON® 828/THF mixture was added the desired amount of EPIKURE® 3270 (amodified aliphatic amine curing agent). All materials were thoroughlymixed and care was taken to ensure that even the material along thesides of the aluminum foil weighing dish was dispersed and mixed. THFwas added in increasing amounts by weight at 1.0%, 5.0%, 10.0%, and 25%,respectively. The total amount of material mixed was kept at ≦17.5 g tominimize the loss of material from the small aluminum weighing dish whenbeing stirred/mixed. Before the material had cured, small amounts werepoured into disk shaped RTV silicone molds (diameter=11 mm, by 3.4 mmdeep). The material in the RTV mold and the material that remained inthe aluminum weighing dish was partially cured at ca. 25° C. overnightin a fume hood. This also allowed most of the THF to volatilize from thesamples. All of the samples were then cured at ˜110° C. for 5 hours. Thesamples were cooled to ca. 25° C. overnight in a fume hood. All of thesamples were then fully cured at ˜110° C. for 5 hours under vacuum. Thelong cure times, high cure temperatures, and exposure to vacuumfacilitated substantially complete removal of the THF from the polymerresin. The samples were finally cooled to ca. 25° C., and tested over aperiod of 2 weeks.

TABLE 1 Model Epoxy with Increasing Amounts of Added THF - Samples Curedat 110° C. for 5 hours and then at 110° C. for 5 hours under vacuum.Amount (g) 1 0% by weight THF EPON ® 828 9.90 EPIKURE ™ 3270 7.43 Total17.33 THF 0 Sum All 17.33 2 1% by weight THF EPON ® 828 9.90 EPIKURE ™3270 7.43 Total 17.33 THF 0.17 Sum All 17.50 3 5% by weight THF EPON ®828 9.50 EPIKURE ™ 3270 7.13 Total 16.63 THF 0.88 Sum All 17.50 4 10% byweight THF EPON ® 828 9.00 EPIKURE ™ 3270 6.75 Total 15.75 THF 1.75 SumAll 17.50 5 25% by weight THF EPON ® 828 7.50 EPIKURE ™ 3270 5.63 Total13.13 THF 4.38 Sum All 17.50

B. Increasing Amounts of THF Added to Model Epoxy—Additional HeatingUnder Vacuum

Model epoxy formulations, prepared according to the procedure describedin 1A above, were subjected to further testing. Before the material hadcured, small amounts were poured into disk shaped RTV silicone molds, asdescribed above. The material in the RTV mold and the material thatremained in the aluminum weighing dish was cured at ca. 25° C. overnightin a fume hood. This also allowed most of the THF to volatilize. All ofthe samples were then cured at ˜110° C. for 5 hours. The samples werethen cooled to ca. 25° C. overnight in a fume hood, followed by curingat ˜110° C. for 5 hours under vacuum. After a period of 2 weeks at ca.25° C., all of the samples were then heated at ˜110° C. for 48 hoursunder vacuum. The excessive cure times, high cure temperatures, andexposure to vacuum facilitated substantially complete removal of the THFfrom the polymer.

C. Increasing Cure Times for Model Epoxy without Added THF

A series of identical model epoxy formulations were prepared andsubjected to increasing cure times from 1 to 9 hours at 110° C. THF wasnot added to these samples. The samples were prepared by weighing thedesired amount of EPON® 828 into a small aluminum weighing dish, towhich was added the EPIKURE® 3270 (Table 2). The materials werethoroughly mixed and care was taken to ensure that even the materialalong the sides of the aluminum foil weighing dish was dispersed andmixed. The total amount of material mixed was kept at ≦17.5 g tominimize the loss of material from the small aluminum weighing dish whenbeing stirred/mixed. Before the material had cured, small amounts werepoured into disk shaped RTV silicone molds. The material in the RTV moldand the material that remained in the aluminum weighing dish waspartially cured at ca. 25° C. overnight in a fume hood. All of thesamples were then cured at ˜110° C. from 1 to 9 hours. The sample curedfor 7 hours was cured under vacuum for the last 2 hours of the 7 hoursof total cure time. The sample cured for 9 hours was cured under vacuumfor the last 4 hours of the 9 hours of total cure time. The samples werethen cooled to ca. 25° C. overnight in a fume hood. The samples weretested over a period of 2 weeks.

TABLE 2 Model Epoxy cured from 1 to 9 hours 110° C. Amount (g) 1 1 hr at110° C. EPON ® 828 10.00 EPIKURE ™ 3270 7.50 Total 17.50 2 2 hrs at 110°C. EPON ® 828 10.00 EPIKURE ™ 3270 7.50 Total 17.50 3 3 hrs at 110° C.EPON ® 828 10.00 EPIKURE ™ 3270 7.50 Total 17.50 4 5 hrs at 110° C.EPON ® 828 10.00 EPIKURE ™ 3270 7.50 Total 17.50 5 7 hrs (2 undervacuum) at 110° C. EPON ® 828 10.00 EPIKURE ™ 3270 7.50 Total 17.50 6 9hrs (2 under vacuum) at 110° C. EPON ® 828 10.00 EPIKURE ™ 3270 7.50Total 17.50

Example 2 Polyurethane A. Increasing Amounts of THF Added toPolyurethane

A series of urethane formulations were prepared with increasing amountsof THF. A control sample without THF was also made. The samples wereprepared by weighing the desired amount of diol chain extenders (CytecCONATHANE® EN-8 Part B) into a small aluminum weighing dish, to whichwas added the desired amount of THF (Table 3). The THF was carefullymixed into the EN8 Part B using a wooden tongue depressor that had beensplit the long way. Care was taken in mixing to minimize the evaporationof THF. Next, a polyurethane (Cytec CONATHANE® EN4 Part A) was added tothe EN8 Part B/THF mixture. All materials were thoroughly mixed and carewas taken to ensure that even the material along the sides of thealuminum foil weighing dish was dispersed and mixed. THF was added inincreasing amounts by weight at 1.0%, 2.5%, 5.0%, 10.0%, and 25%. Thetotal amount of material mixed was kept at ≦17.5 g to minimize the lossof material from the small aluminum weighing dish when beingstirred/mixed. Before the material cured, small amounts were poured intodisk-shaped RTV silicone molds. The material in the RTV mold and thematerial that remained in the aluminum weighing dish was partially curedat ca. 25° C. overnight in a fume hood. This also allowed most of theTHF to volatilize. All of the samples were then cured at ˜110° C. for 5hours. The samples were then cooled to ca. 25° C. overnight in a fumehood, and then cured at ˜110° C. for 5 hours under vacuum. The long curetimes, high cure temperatures, and exposure to vacuum facilitatedsubstantially complete removal of the THF. The samples were then cooledto ca. 25° C. and tested over a period of 2 weeks.

TABLE 3 Polyurethane with Increasing Amounts of Added THF. Amount (g) 00% by weight THF EN4 (Part A) 14.58 EN8 (Part B) 2.74 Total 17.32 THF 0Sum All 17.32 1 1% by weight THF EN4 (Part A) 14.58 EN8 (Part B) 2.74Total 17.32 THF 0.17 Sum All 17.50 2 2.5% by weight THF EN4 (Part A)14.36 EN8 (Part B) 2.70 Total 17.06 THF 0.44 Sum All 17.50 3 5% byweight THF EN4 (Part A) 14.00 EN8 (Part B) 2.63 Total 16.63 THF 0.88 SumAll 17.51 4 10% by weight THF EN4 (Part A) 13.25 EN8 (Part B) 2.49 Total15.74 THF 1.75 Sum All 17.49 5 25% by weight THF EN4 (Part A) 11.05 EN8(Part B) 2.08 Total 13.13 THF 4.38 Sum All 17.50B. Increasing Cure Times for Polyurethane without Added THF

A series of identical EN8 urethane formulations were prepared andsubjected to increasing cure times from 1 to 9 hours at 110° C. THF wasnot added to these samples. The samples were prepared by weighing thedesired amount of EN8 Part B into a small aluminum weighing dish, towhich was added the desired amount of EN4 (Table 4). The materials werethoroughly mixed and care was taken to ensure that even the materialalong the sides of the aluminum foil weighing dish was dispersed andmixed. The total amount of material mixed was kept at ≦17.82 g tominimize the loss of material from the small aluminum weighing dish whenbeing stirred/mixed. Before the material had cured, small amounts werepoured into disk shaped RTV silicone molds. The material in the RTV moldand the material that remained in the aluminum weighing dish was curedat ca. 25° C. overnight in a fume hood. All of the samples were thencured at ˜110° C. from 1 to 9 hours. The sample cured for 7 hours wascured under vacuum for the last 2 hours of the 7 hours of total curetime. The sample cured for 9 hours was cured under vacuum for the last 4hours of the 9 hours of total cure time. The samples were cooled to ca.25° C. overnight in a fume hood. The samples were tested over a periodof 2 weeks.

TABLE 4 Cytec EN8 Polyurethane Encapsulant cured from 1 to 9 hours at110° C. Amount (g) 1 1 hr at 110° C. EN4 (Part A) 15.00 EN8 (Part B)2.82 Total 17.82 2 2 hrs at 110° C. EN4 (Part A) 15.00 EN8 (Part B) 2.82Total 17.82 3 3 hrs at 110° C. EN4 (Part A) 15.00 EN8 (Part B) 2.82Total 17.82 4 5 hrs at 110° C. EN4 (Part A) 15.00 EN8 (Part B) 2.82Total 17.82 5 7 hrs (2 under vacuum) at 110° C. EN4 (Part A) 15.00 EN8(Part B) 2.82 Total 17.82 6 9 hrs (2 under vacuum) at 110° C. EN4(PartA) 15.00 EN8 (Part B) 2.82 Total 17.82

Example 3 Material Characterization A. Rheology

All rheology testing was performed on a TA Aries 2000 or AR-G2 rheometerunder torsion between 25-mm parallel plates. As much as possible, disks(diameter ˜11 mm, by ˜3.4 mm) of uniform size were used as samples.Samples that where thicker than ˜3.2 mm were sanded with an ultra-finegrit sand paper. All samples were subjected to a temperature sweep fromlow to high temperatures at strains of 0.025% and a frequency of 1 Hz.All experiments where performed under normal force control at 5.0 N,with a 0.5 N tolerance (gap=+/−500,000 nm). The temperature range varieddepending on the locations of the expected transitions, but a 5 minuteequilibration time was used once a sample reached the minimumtemperature. A temperature ramp rate of 3° C./min. was used. Rheology isused to determine, among other things, the glass transition temperature(Tg) of a given material. The Tg is determined as being the maximum Tanδ peak height.

B. Thermogravimetric Analysis (TGA)

Thermogravimetric analysis was performed on clean Pt pans using a TAQ1000 instrument. All experiments were performed using a ramp rate of10° C./min. over the desired temperature range. All experiments whereperformed under nitrogen.

Example 4 Observations A. Model Epoxy (EPON® 828+EPIKURE® 3270)

1. Example 1A-Rheology

Even though the samples from Example 1A were cured at 110° C. for 5hours and then at 110° C. for 5 hours under vacuum to remove THF, the Tgsteadily decreased as the amount of THF present during the partialcuring process was increased. The Tg decreased by up to about 20° C.when 25 wt % THF is added to the epoxy formulation compared to thecontrol. The vast majority of the THF originally present while the epoxycured is removed under these curing parameters, although trace amountsmay still remain. The results are shown in FIG. 1.

2. Example 1B-Rheology

The samples from Example 1B were subjected to an additional 48 hoursunder vacuum at 110° C., in addition to being cured at 110° C. for 5hours and then at 110° C. for 5 hours under vacuum. This curing processwas designed to remove even more of any residual THF that may bepresent. However, the Tg of the polymer was still steadily decreased asthe amount of THF present during the partial curing process wasincreased. The Tg still decreased by about 15° C. when 25 wt % THF isadded to the epoxy formulation compared to the control. The results areshown in FIG. 2.

3. Example 1B-TGA

When the Model Epoxy samples from Example 1B, were tested by TGA, nodiscernible increase in weight loss was observed for the samples thathad been treated with THF compared to the control. If anything, thesamples that had been treated with THF exhibited less weight losscompared to the control. The presence of any residual THF did not appearto change the thermal stability of the model epoxies. The results areshown in FIG. 3.

4. Examples 1A and 1B-Mass Spectrometry for Residual THF Analysis

Although not quantitative, Mass Spectrometry was used to determine ifresidual THF was present in both the Model Epoxy samples from Examples1A and 1B. The samples were outgassed over a temperature range of 35° C.to 400° C. and analyzed by direct insertion probe mass spectrometry. Forthe samples from Example 1A, no THF or just the mass of THF was detectedin sample treated with <1 wt % THF. At 5 wt %, THF could be detected inthe total ion chromatogram. At >10 wt %, THF was clearly detected.However, for the samples from Example 1B, no THF or just the mass of THFwas detected in samples treated with <5 wt % THF. At 10 wt % THF, THFcould be detected in the total ion chromatogram. At 25 wt % THF, THF wasclearly detected. It was surprisingly determined that the Tg of theresulting polymers prepared in Example 1 was permanently lowered throughthis inventive process even though only trace amounts (if any) THFremained in the sample.

5. Example 1C-Rheology

Curing the Model Epoxy samples from Example 1C for increasing amounts oftime at 110° C. caused only a small drop in the Tg. However, the Tgappears to have stopped dropping after 5 hours at 110° C. and the totaldrop in the Tg (<10° C.) is smaller than the drop in the Tg when 25 wt %of THF is present during partial curing and then later almost entirelyremoved upon heating and the application of vacuum. This establishesthat the curing regimen itself is not responsible for the change in Tg.The results are shown in FIGS. 4-5.

B. Cytec Conathane® EN8 Polyurethane

1. Example 2A-Rheology

The Tg of EN8 urethane behaves similarly to the Model Epoxy, althoughthe drop in the Tg is smaller and only appears to significantly affectone of EN8's two main transitions. The lower temperature Tg, which iscaused by the soft polybutadiene segments within EN8, is not affected bythe addition and subsequent removal of THF. However, the highertemperature transition, which is due to the urethane component of EN8,does exhibit a lowering of its Tg. It is especially noticeable on thehigh temperature tail of the transition. This edge of the Tg can be seento be moving to lower and lower temperatures as the amount of THFpresent when the urethane cures, but is later almost entirely removedupon heating and the application of vacuum. The results are shown inFIG. 6.

2. Example 2B-Rheology

When EN8 urethane is cured for increasing amounts of time at 110° C., nodiscernible change, including a decrease, is observed for either ofEN8's two main Tan δ transitions. This establishes that the curingprocess itself is not responsible for the change in Tg. The results areshown in FIG. 7.

1. A method of lowering the glass transition temperature of a polymericcompound relative to a control polymeric compound, said controlpolymeric compound having a first glass transition temperature, saidmethod comprising: (a) providing a precursor composition, saidcomposition comprising precursor compounds to said polymeric compounddispersed or dissolved in a solvent system, said precursor compoundsbeing selected from the group consisting of monomers, chain extenders,oligomers, pre-polymers, polymers, and combinations thereof; (b) curingsaid precursor compounds in the presence of said solvent system to yielda cured polymer network or partially cured polymer resin; (c)substantially removing said solvent system from said cured polymernetwork to yield a cured polymeric compound or from said partially curedpolymer resin to yield a dried polymer resin; and (d) optionally,further curing said dried polymer resin to yield a cured polymericcompound, wherein said cured polymeric compound has a second glasstransition temperature that is lower than said first glass transitiontemperature.
 2. The method of claim 1, said cured polymer network orpartially cured polymer resin being swollen with said solvent system. 3.The method of claim 1, wherein said precursor compound is selected fromthe group consisting of epoxies, urethanes, silicones, cyanoacrylates,vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde,urea-formaldehyde, imides, esters, cyanate esters, allyl resins, andcombinations thereof.
 4. The method of claim 1, wherein said precursorcomposition comprises from about 50% to about 99.9% by weight of saidprecursor compounds, based upon the total weight of the compositiontaken as 100% by weight.
 5. The method of claim 1, wherein said solventsystem has a boiling point that is from about 25° C. to about the T₅temperature of said cured polymeric compound.
 6. The method of claim 1,wherein said solvent system includes a solvent selected from the groupconsisting of acetic acid, acetic acid anhydride, acetone, acetonitrile,benzene, iso-butanol, n-butanol, tert-butanol, carbon tetrachloride,chlorobenzene, chloroform, cyclohexane, cyclopentane, dichloromethane,dioxane, ethanol, ethyl acetate, ethylene dichloride, heptane, n-hexane,hydrochloric acid, methyl ethyl ketone, methanol, methyl tert-butylether, iso-propanol, n-propanol, pyridine, tetrahydrofuran, toluene,trifluoroacetic acid, water, dimethyl acetamide, dimethyl formamide,pentane, diethyl ether, dimethyl sulfoxide, ethyl ether, ethyleneglycol, petroleum ether, and mixtures thereof.
 7. The method of claim 1,wherein said precursor composition comprises from about 0.1% to about50% by weight of said solvent system, based upon the total weight of thecomposition taken as 100% by weight.
 8. The method of claim 1, whereinsaid precursor composition further comprises an additional ingredientselected from the group consisting of curing agents, fillers,nanofillers, catalysts, processing aids, binders, pigments,antioxidants, antifungal agents, metal oxides, plasticizer, andcombinations thereof.
 9. The method of claim 1, wherein said curing (a)comprises subjecting said composition to ambient temperature andpressure for a time period of from about 0.1 to about 10 hours.
 10. Themethod of claim 1, wherein said further curing (d) comprises subjectingsaid composition to elevated temperature for a time period of from about0.5 to about 48 hours.
 11. The method of claim 1, wherein said removing(c) comprises heat, vacuum pressure, CO₂ extraction, freeze-drying,lyophilization, sublimation, centrifugation, or any combination thereofto remove said solvent system.
 12. The method of claim 1, wherein saidremoving (c) comprises heating said cured polymer network or partiallycured resin to a temperature greater than or equal to the boiling pointof said solvent system for a time period of from about 0.5 to about 48hours.
 13. The method of claim 1, wherein said further curing (d)comprises heating said dried polymer resin to a temperature of fromabout 25° C. to about 300° C., for a time period of from about 0.5 toabout 48 hours.
 14. The method of claim 13, wherein said curing (b)further comprises cooling said polymer resin or network under ambientconditions for a time period of from about 0.1 to about 24 hours toyield a cooled resin or network.
 15. The method of claim 14, furthercomprising reheating said cooled resin or network to a temperature offrom about 25° C. to about the T₅ temperature of the polymeric compound,for a time period of from about 0.5 to about 48 hours to yield saidcured polymeric compound.
 16. The method of claim 1, further comprisingsubjecting said cured polymeric compound to heat, vacuum pressure, or acombination thereof.
 17. The method of claim 1, further comprisingpouring said precursor composition into a mold prior to said curing. 18.The method of claim 1, wherein said cured polymeric compound isessentially free of plasticizer.
 19. An article of manufacturecomprising a polymeric compound, said polymeric compound having adecreased glass transition temperature relative to the glass transitiontemperature of a control polymeric compound, wherein said polymericcompound is essentially free of plasticizer.
 20. The article of claim19, wherein said polymeric compound is a thermoset selected from thegroup consisting of epoxies, urethanes, silicones, cyanoacrylates,vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde,urea-formaldehyde, polyimides, polyesters, cyanate esters, allyl resins,and combinations thereof.
 21. The article of claim 19, wherein saidarticle of manufacture is selected from the group consisting of moldedarticles, pads, o-rings, gaskets, mats, cushions, foams, fibers, fabric,hoses, tubing, belts, tires, and bladders.